The present invention is directed to a pneumatic control for automatically shutting off flow of liquid product supply to a container upon sensing that the container is filled.
There are various known automatic container filling machines wherein a sensing tube extends into a container to be filled and when the lower end of the tube is blocked by the product in the container, back pressure through the tube actuates a control device to stop the flow of product into the container. For example, in U.S. Pat. No. 3,783,913, Trusselle discloses an intricate series of valved nozzles or jets which operate in conjunction with diaphragms and trip valves in order to respond to a sensed back pressure to shut off liquid to the filling container. Another control for such a filling apparatus is disclosed in U.S. Pat. No. 4,832,093 (Morrone) in which back pressure is used to trigger an interface valve which in turn pilots a control valve to shut down the supply of fluid to the container being filled. The control circuit of the Morrone patent employs only a single air pressure source. It is an object of the present invention to provide a set of control elements which achieve improved accuracy of response to a sensed back pressure.